In some situations during the course of commercial and military demolition operations, it is imperative to have substantially simultaneous detonation of several explosive charges which are not in close proximity to each other. Further, it is desirable that these devices do not require any physical connections between them, that they need not require line of sight location, nor that magnetic waves interfere with their operation. This allows the operator to place the charges faster and conceal them better, thereby reducing the possibility of enemy detection.
In the past, if an operator wished to destroy a subject (e.g., a bridge), the operator would distribute charges throughout the supporting members of the bridge. These charges would then be connected with a detonation cord or wire which would be strung from one charge to another. The detonation cord and wire had two negative characteristics. The first was that it took time to string the cord or wire. This forced the operator to spend an inordinate amount of time stringing the cord or wire; the operator was thereby less efficient and exposed to possible detection by unfriendly forces for a greater time period. The second detrimental characteristic was the detection of the detonation cord or wire; as the cord or wire was strung from one charge to another, it was difficult to conceal. Thus detection of the explosive before detonation became quite probable in military operations.
A second method of detonating devices includes remote blasting systems. An example of this method is in U.S. Pat. No. 4,615,268. This method uses an electromagnetic wave to induce AC currents in the receiving unit. Upon receiving the electromagnetic wave, the receiving unit detonates a blasting cap which in turn detonates a charge. Although this method does not use detonation cord, it is susceptible to electromagnetic interferences. For instance, if the object the operator wished to remove was a radio tower, it was possible that the tower itself would interfere with the detonation method.
The U.S. Army has a device designated as the M1 Concussion Detonator. The M1 Concussion Detonator is a mechanical firing device actuated by the concussion wave of a nearby blast. It fires several charges simultaneously without connecting them with wire or detonating cord. A single charge detonated in water or air will detonate all charges primed with the concussion detonators within a particular range of the main charge or of each other. This device has two major drawbacks. The first is that it requires line of sight between each charge in order to operate. The second is that the maximum range in air is only 25.2 feet thus severely limiting the device. Another drawback is that the Ml is unable to discriminate between particular types of signals, as the Ml is dependent upon signal strength only.
This invention overcomes the problems of the prior art. This invention does not require physical connections between each of the charges, yet allows them to detonate substantially simultaneously. However, unlike the remote blasting system, this invention is not affected by electromagnetic waves. This invention operates by sensing the acoustic wave generated by the explosion of a primary charge. Further, it has a much larger range than the Ml and does not require a line of sight placement due to the characteristics of an acoustic signal. Further, unlike the Ml, this invention is capable of discriminating between different signals, thus lessening the chance of a false detonation.